strat-chatbot/config/container.py

"""Dependency wiring — the single place that constructs all adapters.

create_app() is the composition root for the production runtime.  Tests use
the make_test_app() factory in tests/adapters/test_api.py instead (which
wires fakes directly into app.state, bypassing this module entirely).

Why a factory function instead of module-level globals
-------------------------------------------------------
- Makes the lifespan scope explicit: adapters are created inside the lifespan
  context manager and torn down on exit.
- Avoids the singleton-state problems that plague import-time construction:
  tests can call create_app() in isolation without shared state.
- Follows the hexagonal architecture principle that wiring is infrastructure,
  not domain logic.
"""

import logging
from contextlib import asynccontextmanager
from typing import AsyncIterator

from fastapi import FastAPI

from adapters.inbound.api import router
from adapters.outbound.chroma_rules import ChromaRuleRepository
from adapters.outbound.gitea_issues import GiteaIssueTracker
from adapters.outbound.openrouter import OpenRouterLLM
from adapters.outbound.sqlite_convos import SQLiteConversationStore
from config.settings import Settings
from domain.services import ChatService

logger = logging.getLogger(__name__)


def _make_lifespan(settings: Settings):
    """Return an async context manager that owns the adapter lifecycle.

    Accepts Settings so the lifespan closure captures a specific configuration
    instance rather than reading from module-level state.
    """

    @asynccontextmanager
    async def lifespan(app: FastAPI) -> AsyncIterator[None]:
        # ------------------------------------------------------------------
        # Startup
        # ------------------------------------------------------------------
        logger.info("Initialising Strat-Chatbot...")
        print("Initialising Strat-Chatbot...")

        # Ensure required directories exist
        settings.data_dir.mkdir(parents=True, exist_ok=True)
        settings.chroma_dir.mkdir(parents=True, exist_ok=True)

        # Vector store (synchronous adapter — no async init needed)
        chroma_repo = ChromaRuleRepository(
            persist_dir=settings.chroma_dir,
            embedding_model=settings.embedding_model,
        )
        rule_count = chroma_repo.count()
        print(f"ChromaDB ready at {settings.chroma_dir} ({rule_count} rules loaded)")

        # SQLite conversation store
        conv_store = SQLiteConversationStore(db_url=settings.db_url)
        await conv_store.init_db()
        print("SQLite conversation store initialised")

        # LLM adapter — only constructed when an API key is present
        llm: OpenRouterLLM | None = None
        if settings.openrouter_api_key:
            llm = OpenRouterLLM(
                api_key=settings.openrouter_api_key,
                model=settings.openrouter_model,
            )
            print(f"OpenRouter LLM ready (model: {settings.openrouter_model})")
        else:
            logger.warning(
                "OPENROUTER_API_KEY not set — LLM adapter disabled. "
                "POST /chat will return HTTP 503."
            )
            print(
                "WARNING: OPENROUTER_API_KEY not set — "
                "POST /chat will return HTTP 503."
            )

        # Gitea issue tracker — optional
        gitea: GiteaIssueTracker | None = None
        if settings.gitea_token:
            gitea = GiteaIssueTracker(
                token=settings.gitea_token,
                owner=settings.gitea_owner,
                repo=settings.gitea_repo,
                base_url=settings.gitea_base_url,
            )
            print(
                f"Gitea issue tracker ready "
                f"({settings.gitea_owner}/{settings.gitea_repo})"
            )

        # Compose the service from its ports
        service = ChatService(
            rules=chroma_repo,
            llm=llm,  # type: ignore[arg-type]  # None is handled at the router level
            conversations=conv_store,
            issues=gitea,
            top_k_rules=settings.top_k_rules,
        )

        # Expose via app.state for the router's Depends helpers
        app.state.chat_service = service
        app.state.rule_repository = chroma_repo
        app.state.config_snapshot = {
            "openrouter_model": settings.openrouter_model,
            "top_k_rules": settings.top_k_rules,
            "embedding_model": settings.embedding_model,
        }

        print("Strat-Chatbot ready!")
        logger.info("Strat-Chatbot ready")

        yield

        # ------------------------------------------------------------------
        # Shutdown — release HTTP connection pools
        # ------------------------------------------------------------------
        logger.info("Shutting down Strat-Chatbot...")
        print("Shutting down...")

        if llm is not None:
            await llm.close()
            logger.debug("OpenRouterLLM HTTP client closed")

        if gitea is not None:
            await gitea.close()
            logger.debug("GiteaIssueTracker HTTP client closed")

        logger.info("Shutdown complete")

    return lifespan


def create_app(settings: Settings | None = None) -> FastAPI:
    """Construct and return the production FastAPI application.

    Args:
        settings: Optional pre-built Settings instance.  When *None* (the
            common case), a new Settings() is constructed which reads from
            environment variables and the .env file automatically.

    Returns:
        A fully-wired FastAPI application ready to be served by uvicorn.
    """
    if settings is None:
        settings = Settings()

    app = FastAPI(
        title="Strat-Chatbot",
        description="Strat-O-Matic rules Q&A API",
        version="0.1.0",
        lifespan=_make_lifespan(settings),
    )

    app.include_router(router)

    return app